1. Field of the Invention
The present invention relates generally to broadband light sources and, more specifically, to generating supercontinuum in a chalcogenide fiber.
2. Description of the Prior Art
Supercontinuum generation is the process whereby one or more pump sources passing through a medium generates broadband light through a number of nonlinear processes such as modulation instability, four wave mixing, self phase modulation and Raman shifting. Typically, the light generated has a bandwidth many times greater than the bandwidth of the input pump source or sources.
Chalcogenide fiber is fiber composed of the chalcogen elements, sulfur, selenium, and tellurium. Typically, other elements are added to stabilize the glass. Arsenic sulfide (As2S3), arsenic selenide (As2Se3), germanium arsenic sulfide, and germanium arsenic selenide are examples of chalcogenide glass.
Optical fiber consists of a core surrounded by one or more claddings. Light travels in the core and is confined by the index difference between the core and cladding. Microstructured fiber or photonic crystal fiber is a fiber whereby the cladding or claddings comprise a geometric arrangement of air holes in the cladding glass
U.S. Pat. No. 7,133,590 to Shaw teaches a method of generating supercontinuum in a chalcogenide fiber, either conventional core/clad fiber of microstructured photonic crystal fiber within the range of 2 to 14 μm by launching pump light into a chalcogenide fiber whereby the input pump light is broadened by several nonlinear mechanisms in said fibers. However, the method of Shaw is low power, cannot accommodate all fiber, requires large fs Ti:sapphire/OPA for pumping, and pumps in the anomalous dispersion region of fiber. U.S. Pat. No. 7,519,253 to Islam teaches a system and method to generate a broadband supercontinuum in either chalcogenide, fluoride, or tellurite fiber with a pump light consisting of a short pulse laser diode with wavelength of shorter than 2.5 μm and pulse width of at least 100 ps with one or more optical amplifiers chains and a nonlinear fiber with anomalous dispersion at the diode wavelength that modulates the diode through modulation instability. However, the method of Islam requires an initial seed pulse duration of greater than 100 ps and pumps in the anomalous dispersion region of fiber.
What is needed but not present in the prior art is a method of generating supercontinuum in a chalcogenide fiber with a pump light comprising a short pulse fiber laser or diode laser that is wavelength shifted, amplified, and launched into a chalcogenide fiber to generate a broadband spectrum within the mid-IR from a wavelength of 1.5 μm to greater than 5 μm.